Adjusting log size in a static logical volume

ABSTRACT

A method, system, and program for adjusting the size of a file system and an inline file system log housed in a static logical volume. A computer system includes a logical volume allocated between an file system and its inline file system log. A request is received to adjust the inline log from a current size to a new size while maintaining the size of the logical volume. Storage space is then allocated from within the logical volume to the inline log according to the storage requirement for the new size. Allocating storage space may require decreasing or increasing the amount of storage formerly allocated to the inline log. Then, the inline log is reformatted to the allocated storage space, such that the storage allocated to the inline log for a file system is adjusted while the size of the logical volume housing the inline log and file system remains static.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to improved logical volumemanagement and in particular to improved adjustment of storageallocation within a logical volume. Still more particularly, the presentinvention relates to adjusting the storage space allocated between afile system and its file system log housed in a static logical volume.

2. Description of the Related Art

Most data processing systems include a data management system formanaging the storage of files within the physical storage mediaavailable to the data processing system. In particular, data managementsystems may manage the storage of data files in file systems organizedwithin logical volumes. Logical volumes include pages of physicalstorage media organized to appear as a contiguous data storage device,even though in reality the physical pages are not contiguous. In a filesystem, a file is traditionally logically subdivided into pages withinthe logical volume.

In addition, a data management system may implement a file system logthat may be stored in the same logical volume as the file system. Thelog may be used to track changes to file system control data, alsocalled metadata, such as blocks allocated, mapping of file allocation tological blocks, directory contents, and other file system related data.The log can be used to help maintain consistency when the metadata ischanged.

When initializing a logical volume, it is typical to assign a minimumnumber of physical pages to the logical volume for file system purposes.Then, if the log for the logical volume is stored in the logical volume,the pages assigned to the logical volume are further allocated among thelog and file system.

While a file system and log may each be allocated a particular portionof the logical volume, the file system and log may each grow to needstorage space larger than the allocated portion. Currently, when the logneeds additional storage space, additional physical pages are added tothe logical volume for the log. In addition, currently, when the filesystem size is insufficient, additional physical pages are added to thelogical volume for the file system.

While adding physical pages to a logical volume is one way ofcompensating for underestimated file system and log needs, addition ofphysical pages is not always available. For example, as is typical, allof the physical pages of the physical storage media may already beallocated among the available logical volumes. Further, it is alsotypical that either the file system or log may have unused storagecapacity, such that when the additional physical pages are added, otherpages already allocated to the logical volume remain unused.

SUMMARY OF THE INVENTION

Therefore, in view of the foregoing, there is a need for a method,system, and program for adjusting the storage space allocated to a filesystem and its log housed within a logical volume without adjusting thesize of the logical volume. In particular, it is advantageous toreallocate storage pages from within a static logical volume to meet thestorage needs of the file system or inline log, rather than allocatingadditional physical pages to the logical volume, particularly whereadditional physical pages are not available or unused storage space isavailable in the logical volume.

According to one embodiment of the present invention, a request isreceived to adjust an inline log for a file system from a current sizeto a new size while maintaining a predetermined size of a logical volumehousing the file system and its log. Pages of storage space areallocated from within the logical volume to the inline log according tothe storage space required for said new size. The inline log is thenreformatted to the allocated storage space within the logical volume,such that the storage space allocated to an inline log for a file systemis adjusted while the total storage space allocated to the logicalvolume remains constant.

The request to adjust an inline log from a current size to a new sizemay be received from a system administrator or received from a filesystem controller. Further, the request to adjust the inline log from acurrent size to a new size may be a result of a request to adjust thesize of the file system within the logical volume.

When storage space is allocated from the logical volume to the inlinelog, the new size of the log may be larger or smaller than the currentsize. Thus, to reallocate storage space from the logical volume to theinline log, the storage allocated to the file system in the logicalvolume may be increased or decreased from the current size of the filesystem.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself however, as well as apreferred mode of use, further objects and advantages thereof, will bestbe understood by reference to the following detailed description of anillustrative embodiment when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a block diagram depicting a computer system in which thepresent method, system, and program may be implemented;

FIG. 2 is a block diagram depicting a logical volume housing a filesystem and its log in accordance with the method, system, and program ofthe present invention;

FIG. 3 is an illustrative representation of the static logical volumehousing an expanded log in accordance with the method, system, andprogram of the present invention;

FIG. 4 is an illustrative representation of the static logical volumehousing a reduced log in accordance with the method, system, and programof the present invention

FIG. 5 depicts a high level logic flowchart of a process and program foradjusting a size of a log housed within a static logical volume inaccordance with the method, system, and program of the present invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIG. 1, there isdepicted one embodiment of a computer system in which the presentmethod, system, and program may be implemented. The present inventionmay be executed in a variety of systems, including a variety ofcomputing systems and electronic devices under a number of differentoperating systems. In general, the present invention is executed in acomputer system that performs computing tasks such as manipulating datain storage that is accessible to the computer system.

Computer system 100 includes a bus 114 or other communication device forcommunicating information within computer system 10, and at least oneprocessing device such as central processing unit (CPU) 112, coupled tobus 114 for processing information. Bus 114 preferably includeslow-latency and higher latency paths that are connected by bridges andadapters and controlled within computer system 100 by multiple buscontrollers. When implemented as a server system, computer system 100typically includes multiple processors designed to improve networkservicing power.

CPU 112 may be a general-purpose processor such as IBM's PowerPC™processor that, during normal operation, processes data under thecontrol of an operating system (OS) 116 and application software 118accessible from a dynamic storage device such as random access memory(RAM) 124 and a static storage device such as Read Only Memory (ROM)120. OS 116 preferably controls the allocation and deallocation ofmemory within computer system 100. In a preferred embodiment, OS 116contains machine executable instructions that when executed on processor112 carry out the operations depicted in the flowcharts of FIG. 5, andothers described herein. Alternatively, the steps of the presentinvention might be performed by specific hardware components thatcontain hardwired logic for performing the steps, or by any combinationof programmed computer components and custom hardware components.

The present invention may be provided as a computer program product,included on a machine-readable medium having stored thereon the machineexecutable instructions used to program computer system 100 to perform aprocess according to the present invention. The term “machine-readablemedium” as used herein includes any medium that participates inproviding instructions to CPU 112 or other components of computer system100 for execution. Such a medium may take many forms including, but notlimited to, non-volatile media, volatile media, and transmission media.Common forms of non-volatile media include, for example, a floppy disk,a flexible disk, a hard disk, magnetic tape or any other magneticmedium, a compact disc ROM (CD-ROM) or any other optical medium, punchcards or any other physical medium with patterns of holes, aprogrammable ROM (PROM), an erasable PROM (EPROM), electrically EPROM(EEPROM), a flash memory, any other memory chip or cartridge, or anyother medium from which computer system 100 can read and which issuitable for storing instructions. In the present embodiment, an exampleof a non-volatile medium is disk space 126 which as depicted is aninternal component of computer system 100, but will be understood toalso be provided by an external device. Volatile media include dynamicmemory such as RAM 124. Transmission media include coaxial cables,copper wire or fiber optics, including the wires that comprise bus 114.Transmission media can also take the form of acoustic or light waves,such as those generated during radio frequency or infrared datacommunications.

Moreover, the present invention may be downloaded as a computer programproduct, wherein the program instructions may be transferred from aremote computer such as a server to requesting computer system 100 byway of data signals embodied in a carrier wave or other propagationmedium via a network link (e.g., a modem or network connection) to acommunications adapter 136 coupled to bus 114. Communications adapter136 provides a two-way data communications coupling to a network linkthat may be connected, for example, to a local area network (LAN), widearea network (WAN), or directly to an Internet Service Provider (ISP).In particular, the network link may provide wired and/or wirelessnetwork communications to one or more networks, such as network 138.Network 138 may refer to the worldwide collection of networks andgateways that use a particular protocol, such as Transmission ControlProtocol (TCP) and Internet Protocol (IP), to communicate with oneanother. Network 138 uses electrical, electromagnetic, or opticalsignals that carry digital data streams. The signals through the variousnetworks and the signals through communication adapter 136, which carrythe digital data to and from computer system 100, are exemplary forms ofcarrier waves transporting the information.

A memory controller 122 interfaces with bus 114 to control the memorywithin computer system 100. OS 116 preferably determines which portionsof memory to allocate and deallocate and sends commands that are thenimplemented within the memory by memory controller 122. In particular,where OS 116 supports a virtual memory system, the memory systemincludes both RAM 124 and disk space 126. RAM 124 preferably includesmultiple memory blocks and for purposes of the present inventionpreferably includes multiple logical memory blocks, such as 256mega-byte (MB) dynamic RAMs (DRAM).

An I/O adapter 128 interfaces with bus 114 to control disk space 126.Disk space 126 may include multiple types of non-volatile storage spaceaccessible from multiple types of I/O devices including, but not limitedto, direct access storage devices (DASD). Disk space 126 is partitionedinto multiple logical volumes by a logical volume manager (LVM) 30. LVM130 may be regarded as being made up of a set of operating systemcommands, library subroutines, or other tools that allow a user toestablish and control logical volume storage. A logical partitionmaintained by LVM 130 may include several direct access storage devices,but to the applications the logical partition appears as a singlestorage device. Each logical volume is further divided into multiplepages. Each page represents a block of storage of fixed or variablesize. LVM 130 controls the physical storage system resources by mappingdata between a simple and flexible logical view of storage space and theactual physical storage system. LVM 130 does this by using a layer ofdevice driver code that runs above traditional device drivers. Asdepicted, LVM 130 is located between OS 116 and application 118, howeverin alternate embodiments, LVM 130 may be incorporated within OS 116 oranother component of computer system 100.

When implemented as a server system, computer system 100 typicallyincludes multiple communication interfaces accessible via multipleperipheral component interconnect (PCI) bus bridges connected to aninput/output controller. In this manner, computer system 100 allowsconnections to multiple network computers.

Further, multiple peripheral components may be added to computer system100, connected to multiple controllers, adapters, and expansion slotscoupled to one of the multiple levels of bus 114. For example, a userinterface adapter 132 connectively enabled on bus 114 provides aninterface for a keyboard and cursor control device, such as a mouse,trackball, or cursor direction keys. In addition, a display adapter 134is connectively enabled on bus 114 for provide an interface forconnecting a monitor or other display for providing visual, tactile, orother graphical representation formats. In alternate embodiments of thepresent invention, additional input and output peripheral adapters andcomponents may be added.

Those of ordinary skill in the art will appreciate that the hardwaredepicted in FIG. 1 may vary. Furthermore, those of ordinary skill in theart will appreciate that the depicted example is not meant to implyarchitectural limitations with respect to the present invention.

With reference now to FIG. 2, there is depicted a block diagram oflogical volume housing a file system and its file system log inaccordance with the method, system, and program of the presentinvention. As illustrated, disk space 126 includes multiple disks 202and 204. The pages of disks 202 and 204 are organized into logical unitsor pages of multiple bytes of storage in a logical volume 206. In theexample, logical volume 206 is organized in multiple partitions, howeverit will be understood that logical volume 206 may be organized in asingle partition.

In particular, LVM 130 arranges the physical storage systems of diskspace 126 into volume groups in order to give the impression thatlogical volume 206 is a single voluminous disk space. Each logicalvolume in a logical volume group is divided into logical partitions.Likewise, each physical volume in a volume group is divided intophysical partitions. Each logical partition corresponds to at least onephysical partition of disk space 126. But, although the logicalpartitions in a logical volume are numbered consecutively or appear tobe contiguous to each other, the physical partitions to which they eachcorrespond, need not be contiguous to each other. And indeed, mostoften, the physical partitions are not contiguous to each other.

One partition of logical volume 206 is illustrated at reference numeral210. The partition includes an inline log 212 and a file system 214. Log212 preferably tracks the directory for file system 214. In addition,log 212 contains other file system control data such as the blocksallocated within the logical volume, the mapping of file allocation tological blocks, and other related information. Thus, one of the manytasks of LVM 130 is updating log 212 with the mapping and otherinformation for file system 214.

Referring now to FIG. 3, there is depicted an illustrativerepresentation of the static logical volume housing an expanded log inaccordance with the method, system, and program of the presentinvention. As illustrated, a logical volume 302 houses a file system andits log. In the example, logical volume 302 is initially allocated with12 MB of disk space. It will be understood that in alternateembodiments, logical volume 302 may be a logical volume of an alternatesize.

In the example, 1 MB of disk space is originally allocated to the log.After a request to adjust the log to 2 MB, but maintain the size of thelogical volume, the size of the file system is shrunk to 10 MB and thelog size readjusted to 2 MB. Advantageously, multiple types of methodsmay be used to shrink the size of the file system without deleting thedata stored in the file system.

It is important to note that the size of the logical volume may beadjusted, however, as an advantage of the present invention, the size ofthe logical volume remains static while the allocation of storage spaceto the log and to the file system is adjusted within the logical volume.

With reference now to FIG. 4, there is depicted an illustrativerepresentation of the static logical volume with housing a reduced login accordance with the method, system, and program of the presentinvention. As illustrated a logical volume 402 houses a file system andits log. In the example, logical volume 402 is 12 MB. In the example,the log is originally set to 2 MB. After a request to adjust the log to1 MB, but maintain the size of the logical volume, the size of the logis reduced to 1 MB and the remaining storage space is added to the filesystem.

Referring now to FIG. 5, there is depicted a high level logic flowchartof a process and program for adjusting a size of a log housed within astatic logical volume in accordance with the method, system, and programof the present invention. As illustrated, the process started at block500 and thereafter proceeds to block 502. Block 502 depicts adetermination whether a request to change the size of the log, but keepthe logical volume size static is received. If a request is notreceived, then the process iterates at block 502. If a request isreceived, then the process passes to block 504. Block 504 illustratescomparing the new log size requested with the original log size, and theprocess passes to block 506.

Block 506 depicts a determination whether the new log size requested issmaller than the original log size. If the new log size is smaller thanthe original log size, then the process passes to block 510. Block 510depicts giving the unused space to the file system. Next, block 512illustrates reformatting the log to the new size, and the process ends.Alternatively, at block 506, if the new log size is not smaller than theoriginal, then the process passes to block 508. Block 508 depictsshrinking the file system and moving the new space to the log, and theprocess passes to block 512.

While the invention has been particularly shown and described withreference to a preferred embodiment, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention.

1. A method for adjusting the size of an inline log for a file system,comprising: receiving a request to adjust an inline log for a filesystem from a current size to a new size while maintaining a size of alogical volume, wherein said inline log and said file system are storedin said logical volume; allocating storage space from within saidlogical volume to said inline log according to a storage requirement forsaid new size; and reformatting said inline log to said allocatedstorage space, such that said storage space allocated to said inline logfor a file system is adjusted while said size of said logical volumehousing said inline log and said file system remains static.
 2. Themethod according to claim 1 for adjusting the size of an inline log,wherein receiving a request to adjust an inline log further comprises:receiving said request from a system administrator.
 3. The methodaccording to claim 1 for adjusting the size of an inline log, whereinreceiving a request to adjust an inline log further comprises: receivinga first request to adjust said inline log for said file system from saidcurrent size to said new size; detecting that additional storage spaceis not available for allocation to said logical volume; and triggeringsaid request to adjust said inline log for said file system from saidcurrent size to said new size while maintaining said size of saidlogical volume.
 4. The method according to claim 1 for adjusting thesize of an inline log, wherein receiving a request to adjust an inlinelog further comprises: receiving a first request to adjust said filesystem from a current file system size to a new file system size; andtriggering said request to adjust said inline log from said current sizeto said new size to compensate for said first request to adjust saidfile system from said current file system size to a new file systemsize.
 5. The method according to claim 1 for adjusting the size of aninline log, wherein allocating storage space from said logical volume tosaid inline log further comprises: shrinking the total storage spaceallocated to said file system in said logical volume.
 6. The methodaccording to claim 1 for adjusting the size of an inline log, whereinallocating storage space from said logical volume to said inline logfurther comprises: increasing the total storage space allocated to saidfile system in said logical volume.
 7. A system for adjusting the sizeof an inline log for a file system without adjust a size of a logicalvolume storing said inline log and said file system, comprising: meansfor receiving a request to adjust said inline log for said file systemfrom a current size to a new size while maintaining a size of saidlogical volume; means for allocating storage space from within saidlogical volume to said inline log according to a storage spacerequirement for said new size; and means for reformatting said inlinelog to said allocated storage space.
 8. The system according to claim 7for adjusting the size of an inline log, wherein said means forreceiving a request to adjust an inline log further comprises: means forreceiving said request from a system administrator.
 9. The systemaccording to claim 7 for adjusting the size of an inline log, whereinsaid means for receiving a request to adjust an inline log furthercomprises: means for receiving a first request to adjust said inline logfor said file system from said current size to said new size; means fordetecting that additional storage space is not available for allocationto said logical volume; and means for triggering said request to adjustsaid inline log for said file system from said current size to said newsize while maintaining said size of said logical volume.
 10. The systemaccording to claim 7 for adjusting the size of an inline log, whereinsaid means for receiving a request to adjust an inline log furthercomprises: means for receiving a first request to adjust said filesystem from a current file system size to a new file system size; andmeans for triggering said request to adjust said inline log from saidcurrent size to said new size to compensate for said first request toadjust said file system from said current file system size to a new filesystem size.
 11. The system according to claim 7 for adjusting the sizeof an inline log, wherein said means for allocating storage space fromwithin said logical volume to said inline log further comprises: meansfor shrinking the total storage space allocated to said file systemwithin said logical volume.
 12. The system according to claim 7 foradjusting the size of an inline log, wherein said means for allocatingstorage space from within said logical volume to said inline log furthercomprises: means for increasing the total storage space allocated tosaid file system within said logical volume.
 13. A computer programproduct, residing in a computer readable medium, for adjusting the sizeof an inline log for a file system within a static logical volume,comprising: means for receiving a request to adjust said inline log forsaid file system from a current size to a new size while maintaining asize of said logical volume; means for allocating storage space fromwithin said logical volume to said inline log according to a storagerequirement for said new size; and means for reformatting said inlinelog to said allocated storage space.
 14. The computer program productaccording to claim 13 for adjusting the size of an inline log, whereinsaid means for receiving a request to adjust an inline log furthercomprises: means for receiving said request from a system administrator.15. The computer program product according to claim 13 for adjusting thesize of an inline log, wherein said means for receiving a request toadjust an inline log further comprises: means for receiving a firstrequest to adjust said inline log for said file system from said currentsize to said new size; means for detecting that additional storage spaceis not available for allocation to said logical volume; and means fortriggering said request to adjust said inline log for said file systemfrom said current size to said new size while maintaining said size ofsaid logical volume.
 16. The computer program product according to claim13 for adjusting the size of an inline log, wherein said means forreceiving a request to adjust an inline log further comprises: means forreceiving a first request to adjust said file system from a current filesystem size to a new file system size; and means for triggering saidrequest to adjust said inline log from said current size to said newsize to compensate for said first request to adjust said file systemfrom said current file system size to a new file system size.
 17. Thecomputer program product according to claim 13 for adjusting the size ofan inline log, wherein said means for allocating storage space fromwithin said logical volume to said inline log further comprises: meansfor shrinking the total storage space allocated to said file system insaid logical volume.
 18. The computer program product according to claim13 for adjusting the size of an inline log, wherein said means forallocating storage space from within said logical volume to said inlinelog further comprises: means for increasing the total storage spaceallocated to said file system in said logical volume.